I have recently acquired one of these and it does not activate any software within the phone. It does switch on 'car mode' which allows the speaker-phone to activate when a call comes in. I have contacted HTC support and was given this reply,
Sorry for the delayed response. I have investigated the issue a bit further - the Desire does not come with the "NaviPanel” software, as the manufacturer claims, and there is no download available for it. There is a “Navigation” app, which you can find in the list of all apps, but I am not sure if it is the same. Alternatively, you can go to Android market and search for “Car Home” or “Car dock” and try out some of the 3rd party apps available, but please be aware HTC does not produce those, so you will be using them at your own risk.
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I am somewhat annoyed that HTC have stated in the car holder instruction manual and in the original press release, that the 'Navipanel' is activated when the phone is docked. It was a huge selling point for me, as I use the phone in the car more than anything and this feature would have made it easier to operate the phone in the dock.